CA1336005C - Controlled clearance labyrinth seal - Google Patents
Controlled clearance labyrinth sealInfo
- Publication number
- CA1336005C CA1336005C CA000557522A CA557522A CA1336005C CA 1336005 C CA1336005 C CA 1336005C CA 000557522 A CA000557522 A CA 000557522A CA 557522 A CA557522 A CA 557522A CA 1336005 C CA1336005 C CA 1336005C
- Authority
- CA
- Canada
- Prior art keywords
- seal
- seal holder
- housing
- holder
- turbomachinery
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
- 238000000034 method Methods 0.000 claims abstract description 11
- 238000007789 sealing Methods 0.000 claims abstract 4
- 230000004323 axial length Effects 0.000 claims description 16
- 239000012530 fluid Substances 0.000 claims description 11
- 239000000463 material Substances 0.000 description 24
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 5
- 229910052782 aluminium Inorganic materials 0.000 description 5
- 230000008602 contraction Effects 0.000 description 4
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 3
- 239000004020 conductor Substances 0.000 description 3
- 229910052802 copper Inorganic materials 0.000 description 3
- 239000010949 copper Substances 0.000 description 3
- 229910001369 Brass Inorganic materials 0.000 description 2
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 2
- 239000010951 brass Substances 0.000 description 2
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 2
- 229910052737 gold Inorganic materials 0.000 description 2
- 239000010931 gold Substances 0.000 description 2
- 239000011135 tin Substances 0.000 description 2
- 229910052718 tin Inorganic materials 0.000 description 2
- 229910000906 Bronze Inorganic materials 0.000 description 1
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 1
- 229910052787 antimony Inorganic materials 0.000 description 1
- WATWJIUSRGPENY-UHFFFAOYSA-N antimony atom Chemical compound [Sb] WATWJIUSRGPENY-UHFFFAOYSA-N 0.000 description 1
- 229910052785 arsenic Inorganic materials 0.000 description 1
- RQNWIZPPADIBDY-UHFFFAOYSA-N arsenic atom Chemical compound [As] RQNWIZPPADIBDY-UHFFFAOYSA-N 0.000 description 1
- 239000010974 bronze Substances 0.000 description 1
- KUNSUQLRTQLHQQ-UHFFFAOYSA-N copper tin Chemical compound [Cu].[Sn] KUNSUQLRTQLHQQ-UHFFFAOYSA-N 0.000 description 1
- 239000011133 lead Substances 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 239000011777 magnesium Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 230000037361 pathway Effects 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 238000005057 refrigeration Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 239000004332 silver Substances 0.000 description 1
- 239000007779 soft material Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000002277 temperature effect Effects 0.000 description 1
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
- F01D11/00—Preventing or minimising internal leakage of working-fluid, e.g. between stages
- F01D11/02—Preventing or minimising internal leakage of working-fluid, e.g. between stages by non-contact sealings, e.g. of labyrinth type
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16J—PISTONS; CYLINDERS; SEALINGS
- F16J15/00—Sealings
- F16J15/44—Free-space packings
- F16J15/447—Labyrinth packings
- F16J15/4476—Labyrinth packings with radial path
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
- F01D11/00—Preventing or minimising internal leakage of working-fluid, e.g. between stages
- F01D11/02—Preventing or minimising internal leakage of working-fluid, e.g. between stages by non-contact sealings, e.g. of labyrinth type
- F01D11/025—Seal clearance control; Floating assembly; Adaptation means to differential thermal dilatations
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S277/00—Seal for a joint or juncture
- Y10S277/93—Seal including heating or cooling feature
Landscapes
- Engineering & Computer Science (AREA)
- General Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Turbine Rotor Nozzle Sealing (AREA)
- Sealing Using Fluids, Sealing Without Contact, And Removal Of Oil (AREA)
- Structures Of Non-Positive Displacement Pumps (AREA)
Abstract
A method and a labyrinth seal for sealing the gap between the rotating impeller assembly and the stationary housing of turbomachinery comprising a seal holder which serves simultaneously to contact process gas so as to maintain the stationary seal part temperature at about the temperature of the rotating part, thus reducing differential thermal change between the stationary and rotating members of the labyrinth seal.
Description
CONTROLLED CLEARANCE LABYRINTH SEAL
Technical Field This invention relates to labyrinth seals such as are used to form a seal between rotating and stationary parts of turbomachinery.
Backqround Of The Invention Turbomachinery, such as turbocompressors and turboexpanders, are used to process gas from a first pressure to a second pressure and in the process the gas experiences a significant change in temperature. For example, in a turboexpander such as is often used in a cryogenic air separation plant, gas at a high pressure is passed through the turboexpander and expanded to a low pressure, thus experiencing a reduction in temperature and generating refrigeration for the cryogenic process.
Examples of turbomachinery may be found in U.S.
Patent No. 4,430,011 - Kun and U.S. Patent No.
4,472,107 - Chang et al.
Turbomachinery is characterized by a stationary outer housing and a rotatable shaft axially aligned within the housing. Mounted on the shaft are impeller blades through which the gas passes while experiencing the pressure change. The blades are often covered by a shroud for protection and improved performance. The assembly, i.e., shaft, blades and shroud, rotate at a very high speed, typically in excess of 5000 rpm when the turbomachinery is in operation. In order to avoid damage to turbomachinery parts, the rotating assembly within the housing is spaced from the stationary housing.
` D-15,499 ,~
133600~
The space between the rotating assembly and the stationary housing is a source of inefficiency because it provides a pathway for gas to bypass the turbomachine. In order to reduce the amount of gas passing through this spacing, practitioners in this art typically place a seal within the spacing.
Generally the seal is a labyrinth seal.
A labyrinth seal comprises a series of knife-like or tooth-like edges on the rotating part which are adjacent softer seal material on the stationary housing. The edges extend through the spacing between the rotating and stationary elements to nearly contact the stationary element. Thus there is created a series of extremely small annular spaces between the rotating and stationary parts making it very difficult for gas to pass through each of the serial small spaces in order to bypass the turbomachinery.
A common problem with labyrinth seals used in turbomachinery is the tendency of the spacing between the rotating edges and the seal material to change during operation of the turbomachinery due to temperature effects. Due to the significant temperature change of the gas as it passes through the turbomachinery, there is a significant temperature difference between the rotating assembly, which experiences a temperature change in the direction of the gas temperature, and the stationary housing which is at the initial temperature. Thus the edges which are on the rotating assembly are at a different temperature than the seal material which is on the stationary D-15,499 - 3 - 1 33600~
housing. This temperature difference causes the two parts of the labyrinth seal to expand or contract at different rates and this differential thermal movement in the seal parts causes the space between them to change. The larger is the space between the seal parts the greater is the amount of gas which can bypass the turbomachinery and the greater is the efficiency loss experienced. However, spacing which is too close may result in unreliable operation if the parts come into contact.
It is therefore an object of this invention to provide a labyrinth seal for turbomachinery which experiences a reduced differential thermal movement between rotating and stationary seal parts.
Summary Of The Invention The above and other objects which will become apparent to one skilled in the art upon a reading of this disclosure are attained by the present invention which is:
A labyrinth seal for turbomachinery having an impeller shroud rotatably mounted within and spaced from a stationary housing said labyrinth seal comprising: an annular seal holder of heat conductive material attached to the housing but spaced from the housing along its axial length and capable of radial movement with respect to said housing, said seal holder having seal material along at least a portion of its inner axial length, said seal material being adjacent and spaced from a toothed portion of the impeller shroud, said seal holder extending past the edge of the impeller shroud.
D-15,499 - Brief Description Of The Drawinqs Figure 1 is an isometric view of a turbomachinery impeller showing one embodiment of the rotating element of the labyrinth seal of this invention.
Figure 2 is a cross-sectional view of a preferred embodiment of the labyrinth seal of this invention.
Detailed Description The labyrinth seal of this invention will be described in detail with reference to the drawings.
Referring now to Figure 1, turbomachinery impeller 10 comprises shaft 11 upon which are mounted turbine blades 16 enclosed by impeller shroud 12. During operation the impeller rotates about its axial centerline and the gas that is being expanded or compressed will flow through the flow channels formed by the blades and the enclosing shroud. For example, for an expansion turbine, the gas would enter the blades at the outermost radius 13, pass through the flow channels as it expands transferring power to the rotating impeller, and exit at the discharge annulus 14. In the case of a turbocompressor, the flow of fluid would be reversed.
Along at least a portion of the axial length of the shroud and completely around the outside of the shroud is a series of knifelike or toothlike edges 28 which form the rotating element of the labyrinth seal of this invention. In operation, impeller 10 is mounted within and is spaced from a stationary housing which conforms to D-15,499 the shape of the impeller. Toothed portion 28 forms a seal with the stationary elements of the labyrinth seal of this invention in order to restrict the flow of gas between the shroud and the housing thus reducing the amount of gas which can bypass the turbine blades.
Referring now to Figure 2, shroud 12 and stationary housing 29 are spaced apart. In conventional labyrinth seals the toothed portion of the impeller shroud forms a labyrinth seal with seal material on the adjacent portion of the housing. In the labyrinth seal of this invention the seal material is not on the housing but on seal holder 30 which is attached to but otherwise independent from the housing. Seal holder 30 is between shroud 12 and housing 29 in the area of toothed portion 28.
Seal holder 30 is an annular ring which fits around the toothed portion of shroud 12 and extends out past the edge 40 of the shroud 12. Seal holder 30 is attached to housing 29 such as by means of shoulder screws 31 so that it is restrained in the axial direction, but is separate from housing 29 and spaced from housing 29 along at least portion of its axial length. Furthermore the flanged section of seal holder 30 is separated from housing 29 and the heads of shoulder screws 31 by low friction and low thermal conductivity annular slide rings 32.
Along at least a portion of the inner axial length of seal holder 30, adjacent and spaced from toothed portion 28, is seal material 34. Seal material 34 is relatively soft material which serves to reduce damage to toothed portion 28 should there D-15,499 be momentary contact between the rotary and stationary parts of the turbomachinery. Preferably the seal material is lead-based babbitt which is a mixture of 10-15 percent antimony, 2-10 percent tin, up to 0.2 percent copper, with or without arsenic, with the remainder lead. Other materials which may be used for seal material 34 include lead, silver, gold, soft plastics, Micarta and magnesium. The preferred material depends upon its friction characteristics relative to the impeller material and ease of bonding to the seal holder 30.
The operation of the labyrinth seal of this invention will be described with reference to the operation of a turboexpander. In a turboexpander gas passes through the impeller in the direction indicated by arrow 35 in Figure 2 and in the process the gas expands and cools. Thus the impeller including the toothed portion is cooled by the expanding gas and consequently experiences inward thermal contraction. The housing however remains essentially at the inlet gas temperature and thus undergoes less thermal contraction then the impeller. Thus the gap between the impeller assembly and the housing widens. In conventional labyrinth seal arrangements wherein the seal material is on the housing this differential thermal contraction causes the seal gap to widen and allows a greater quantity of process gas to bypass the turbine blades.
In the labyrinth seal of this invention seal holder 30 serves to keep seal material 34 and toothed portion 28 at about the same temperature D-15,499 - 7 ~ 1336 005 thus reducing their thermal contraction differential and keeping the gap between them narrower than would otherwise be the case with a conventional labyrinth seal. Seal holder 30 accomplishes this by extending past edge 40 of shroud 12 so that it comes in thermal contact with cold gas past the impeller exit. Thus the cold gas serves to cool seal holder 30 and causes it to thermally contract in order to maintain a small gap between it and contracting toothed portion 28. Seal holder 30 is made of heat conductive material and thus heat is rapidly passed from one end of seal holder 30 where seal material 34 is located to the other end. Preferably seal holder 30 is made of aluminum. Other suitable heat conductive materials from which seal holder 30 could be made include brass, bronze, copper, tin and gold. However the material for seal holder 30 must be compatible with seal material 34 or an intermediate bonding material to maintain adherence and chemical stability. For example, in the case where the seal holder is made of aluminum, an intermediate layer of copper is prefe-ably electrodeposited to provide a compatible surface for the babbitt.
Extension 41 which is the part of seal holder 30 which extends past edge 40 of shroud 12 should be of sufficient length to provide a large surface area to enable efficient heat transfer from process gas to seal holder 30. Generally the length of extension 41 will be from 25 to 75 percent of that of seal holder 30 and preferably is from 50 to 75 percent. In addition seal holder 30 should have D-15,499 a sufficient thickness, i.e., difference between inside and outside diameter, to enable efficient heat transfer axially along the seal holder length.
Seal holder 30 is capable of radial movement with respect to housing 29. Thus as seal holder 30 contracts inward, the gap between seal holder 30 and housing 29 along their common axial length widens. In order to ensure that seal holder 30 remains concentric with housing 29, conical take-up ring 33 is preferably provided between seal holder 30 and housing 29. Take-up ring 33 acts as a relatively weak spring in the radial direction and as a relatively stiff spring in the transverse direction. As seal holder 30 contracts, the angle of take-up ring 33 increases thus maintaining the concentricity of seal holder 30 along its entire circumference with respect to housing 29 despite their different rates of thermal change.
Specifically, any change in the radial space between seal holder 30 and housing 29 causes a change in a uniform circumferentially distributed toroidal momen~ on the take-up ring cross-section. Since a thin-section ring (cross-sectional area divided by radius squared less than 0.01) will easily roll under such a moment change, there will be very little resistance to the change in the radial space between seal holder 30 and housing 29. Conversely, any tendency for seal holder 30 to shift in the transverse direction relative to housing 29 loads the entire ring in shear. Since the ring 33 is essentially a very short, stiff beam when loaded in shear, the seal holder 30 remains concentric to housing 29.
D-15,499 - 9 - 1 33600~
The following examples are provided for illustrative purposes and are not intended to be limiting.
EXAMPLE I
A turboexpander was provided with a labyrinth seal of this invention similar to that shown in Figure 2. The seal holder was made of brass and had a thickness of one inch between its inner and outer diameters at the extension portion.
lQ The overall axial length of the seal holder was 3 inches and the length of the extension past the shroud edge was 1 1/2 inches. The seal material was lead-based babbitt and the impeller shroud including the toothed portion was aluminum. The impeller operated at 22,500 revolutions per minute (rpm).
Gas at a temperature of 300R and a pressure of 639 psia entered and passed through the turboexpander, and exited the turboexpander at a temperature of 167R and a pressure of 70 psia. The gap between the toothed portion and the seal material was reduced by about 0.0006 inches over the gap that would occur with a conventional labyrinth seal.
This reduction in the seal gap provides an increase in the efficiency of the turboexpander of 0.25 percent.
EXAMPLE II
A turboexpander is provided with a labyrinth seal of this invention similar to that shown in Figure 2. The seal holder is made aluminum and has a thickness of one inch between its inner and outer diameters at the extension portion. The D-15,499 - 10 - 133600a overall axial length of the seal holder is 3 inches and length of the extension past the shroud edge is 1 1/2 inches. The seal material is lead-based babbitt and the impeller shroud including the toothed portion is aluminum. The impeller is operated and gas is passed through the turboexpander as described in Example I. The gap between the toothed portion and the seal material is reduced by about 0.0021 inches over the gap that would occur with a conventional labyrinth seal. This reduction in the seal gap provides an increase in the efficiency of the turboexpander of 0.7 percent.
Now by the use of the labyrinth seal of this invention one can operate turbomachinery with increased efficiency. Although the labyrinth seal of this invention has been described in detail with reference to a specific embodiment and in operation in a turboexpander, those skilled in the art will recognize that there are other embodiments of the labyrinth seal of this invention and that the invention is useful with any type of turbomachinery.
D-15,499
Technical Field This invention relates to labyrinth seals such as are used to form a seal between rotating and stationary parts of turbomachinery.
Backqround Of The Invention Turbomachinery, such as turbocompressors and turboexpanders, are used to process gas from a first pressure to a second pressure and in the process the gas experiences a significant change in temperature. For example, in a turboexpander such as is often used in a cryogenic air separation plant, gas at a high pressure is passed through the turboexpander and expanded to a low pressure, thus experiencing a reduction in temperature and generating refrigeration for the cryogenic process.
Examples of turbomachinery may be found in U.S.
Patent No. 4,430,011 - Kun and U.S. Patent No.
4,472,107 - Chang et al.
Turbomachinery is characterized by a stationary outer housing and a rotatable shaft axially aligned within the housing. Mounted on the shaft are impeller blades through which the gas passes while experiencing the pressure change. The blades are often covered by a shroud for protection and improved performance. The assembly, i.e., shaft, blades and shroud, rotate at a very high speed, typically in excess of 5000 rpm when the turbomachinery is in operation. In order to avoid damage to turbomachinery parts, the rotating assembly within the housing is spaced from the stationary housing.
` D-15,499 ,~
133600~
The space between the rotating assembly and the stationary housing is a source of inefficiency because it provides a pathway for gas to bypass the turbomachine. In order to reduce the amount of gas passing through this spacing, practitioners in this art typically place a seal within the spacing.
Generally the seal is a labyrinth seal.
A labyrinth seal comprises a series of knife-like or tooth-like edges on the rotating part which are adjacent softer seal material on the stationary housing. The edges extend through the spacing between the rotating and stationary elements to nearly contact the stationary element. Thus there is created a series of extremely small annular spaces between the rotating and stationary parts making it very difficult for gas to pass through each of the serial small spaces in order to bypass the turbomachinery.
A common problem with labyrinth seals used in turbomachinery is the tendency of the spacing between the rotating edges and the seal material to change during operation of the turbomachinery due to temperature effects. Due to the significant temperature change of the gas as it passes through the turbomachinery, there is a significant temperature difference between the rotating assembly, which experiences a temperature change in the direction of the gas temperature, and the stationary housing which is at the initial temperature. Thus the edges which are on the rotating assembly are at a different temperature than the seal material which is on the stationary D-15,499 - 3 - 1 33600~
housing. This temperature difference causes the two parts of the labyrinth seal to expand or contract at different rates and this differential thermal movement in the seal parts causes the space between them to change. The larger is the space between the seal parts the greater is the amount of gas which can bypass the turbomachinery and the greater is the efficiency loss experienced. However, spacing which is too close may result in unreliable operation if the parts come into contact.
It is therefore an object of this invention to provide a labyrinth seal for turbomachinery which experiences a reduced differential thermal movement between rotating and stationary seal parts.
Summary Of The Invention The above and other objects which will become apparent to one skilled in the art upon a reading of this disclosure are attained by the present invention which is:
A labyrinth seal for turbomachinery having an impeller shroud rotatably mounted within and spaced from a stationary housing said labyrinth seal comprising: an annular seal holder of heat conductive material attached to the housing but spaced from the housing along its axial length and capable of radial movement with respect to said housing, said seal holder having seal material along at least a portion of its inner axial length, said seal material being adjacent and spaced from a toothed portion of the impeller shroud, said seal holder extending past the edge of the impeller shroud.
D-15,499 - Brief Description Of The Drawinqs Figure 1 is an isometric view of a turbomachinery impeller showing one embodiment of the rotating element of the labyrinth seal of this invention.
Figure 2 is a cross-sectional view of a preferred embodiment of the labyrinth seal of this invention.
Detailed Description The labyrinth seal of this invention will be described in detail with reference to the drawings.
Referring now to Figure 1, turbomachinery impeller 10 comprises shaft 11 upon which are mounted turbine blades 16 enclosed by impeller shroud 12. During operation the impeller rotates about its axial centerline and the gas that is being expanded or compressed will flow through the flow channels formed by the blades and the enclosing shroud. For example, for an expansion turbine, the gas would enter the blades at the outermost radius 13, pass through the flow channels as it expands transferring power to the rotating impeller, and exit at the discharge annulus 14. In the case of a turbocompressor, the flow of fluid would be reversed.
Along at least a portion of the axial length of the shroud and completely around the outside of the shroud is a series of knifelike or toothlike edges 28 which form the rotating element of the labyrinth seal of this invention. In operation, impeller 10 is mounted within and is spaced from a stationary housing which conforms to D-15,499 the shape of the impeller. Toothed portion 28 forms a seal with the stationary elements of the labyrinth seal of this invention in order to restrict the flow of gas between the shroud and the housing thus reducing the amount of gas which can bypass the turbine blades.
Referring now to Figure 2, shroud 12 and stationary housing 29 are spaced apart. In conventional labyrinth seals the toothed portion of the impeller shroud forms a labyrinth seal with seal material on the adjacent portion of the housing. In the labyrinth seal of this invention the seal material is not on the housing but on seal holder 30 which is attached to but otherwise independent from the housing. Seal holder 30 is between shroud 12 and housing 29 in the area of toothed portion 28.
Seal holder 30 is an annular ring which fits around the toothed portion of shroud 12 and extends out past the edge 40 of the shroud 12. Seal holder 30 is attached to housing 29 such as by means of shoulder screws 31 so that it is restrained in the axial direction, but is separate from housing 29 and spaced from housing 29 along at least portion of its axial length. Furthermore the flanged section of seal holder 30 is separated from housing 29 and the heads of shoulder screws 31 by low friction and low thermal conductivity annular slide rings 32.
Along at least a portion of the inner axial length of seal holder 30, adjacent and spaced from toothed portion 28, is seal material 34. Seal material 34 is relatively soft material which serves to reduce damage to toothed portion 28 should there D-15,499 be momentary contact between the rotary and stationary parts of the turbomachinery. Preferably the seal material is lead-based babbitt which is a mixture of 10-15 percent antimony, 2-10 percent tin, up to 0.2 percent copper, with or without arsenic, with the remainder lead. Other materials which may be used for seal material 34 include lead, silver, gold, soft plastics, Micarta and magnesium. The preferred material depends upon its friction characteristics relative to the impeller material and ease of bonding to the seal holder 30.
The operation of the labyrinth seal of this invention will be described with reference to the operation of a turboexpander. In a turboexpander gas passes through the impeller in the direction indicated by arrow 35 in Figure 2 and in the process the gas expands and cools. Thus the impeller including the toothed portion is cooled by the expanding gas and consequently experiences inward thermal contraction. The housing however remains essentially at the inlet gas temperature and thus undergoes less thermal contraction then the impeller. Thus the gap between the impeller assembly and the housing widens. In conventional labyrinth seal arrangements wherein the seal material is on the housing this differential thermal contraction causes the seal gap to widen and allows a greater quantity of process gas to bypass the turbine blades.
In the labyrinth seal of this invention seal holder 30 serves to keep seal material 34 and toothed portion 28 at about the same temperature D-15,499 - 7 ~ 1336 005 thus reducing their thermal contraction differential and keeping the gap between them narrower than would otherwise be the case with a conventional labyrinth seal. Seal holder 30 accomplishes this by extending past edge 40 of shroud 12 so that it comes in thermal contact with cold gas past the impeller exit. Thus the cold gas serves to cool seal holder 30 and causes it to thermally contract in order to maintain a small gap between it and contracting toothed portion 28. Seal holder 30 is made of heat conductive material and thus heat is rapidly passed from one end of seal holder 30 where seal material 34 is located to the other end. Preferably seal holder 30 is made of aluminum. Other suitable heat conductive materials from which seal holder 30 could be made include brass, bronze, copper, tin and gold. However the material for seal holder 30 must be compatible with seal material 34 or an intermediate bonding material to maintain adherence and chemical stability. For example, in the case where the seal holder is made of aluminum, an intermediate layer of copper is prefe-ably electrodeposited to provide a compatible surface for the babbitt.
Extension 41 which is the part of seal holder 30 which extends past edge 40 of shroud 12 should be of sufficient length to provide a large surface area to enable efficient heat transfer from process gas to seal holder 30. Generally the length of extension 41 will be from 25 to 75 percent of that of seal holder 30 and preferably is from 50 to 75 percent. In addition seal holder 30 should have D-15,499 a sufficient thickness, i.e., difference between inside and outside diameter, to enable efficient heat transfer axially along the seal holder length.
Seal holder 30 is capable of radial movement with respect to housing 29. Thus as seal holder 30 contracts inward, the gap between seal holder 30 and housing 29 along their common axial length widens. In order to ensure that seal holder 30 remains concentric with housing 29, conical take-up ring 33 is preferably provided between seal holder 30 and housing 29. Take-up ring 33 acts as a relatively weak spring in the radial direction and as a relatively stiff spring in the transverse direction. As seal holder 30 contracts, the angle of take-up ring 33 increases thus maintaining the concentricity of seal holder 30 along its entire circumference with respect to housing 29 despite their different rates of thermal change.
Specifically, any change in the radial space between seal holder 30 and housing 29 causes a change in a uniform circumferentially distributed toroidal momen~ on the take-up ring cross-section. Since a thin-section ring (cross-sectional area divided by radius squared less than 0.01) will easily roll under such a moment change, there will be very little resistance to the change in the radial space between seal holder 30 and housing 29. Conversely, any tendency for seal holder 30 to shift in the transverse direction relative to housing 29 loads the entire ring in shear. Since the ring 33 is essentially a very short, stiff beam when loaded in shear, the seal holder 30 remains concentric to housing 29.
D-15,499 - 9 - 1 33600~
The following examples are provided for illustrative purposes and are not intended to be limiting.
EXAMPLE I
A turboexpander was provided with a labyrinth seal of this invention similar to that shown in Figure 2. The seal holder was made of brass and had a thickness of one inch between its inner and outer diameters at the extension portion.
lQ The overall axial length of the seal holder was 3 inches and the length of the extension past the shroud edge was 1 1/2 inches. The seal material was lead-based babbitt and the impeller shroud including the toothed portion was aluminum. The impeller operated at 22,500 revolutions per minute (rpm).
Gas at a temperature of 300R and a pressure of 639 psia entered and passed through the turboexpander, and exited the turboexpander at a temperature of 167R and a pressure of 70 psia. The gap between the toothed portion and the seal material was reduced by about 0.0006 inches over the gap that would occur with a conventional labyrinth seal.
This reduction in the seal gap provides an increase in the efficiency of the turboexpander of 0.25 percent.
EXAMPLE II
A turboexpander is provided with a labyrinth seal of this invention similar to that shown in Figure 2. The seal holder is made aluminum and has a thickness of one inch between its inner and outer diameters at the extension portion. The D-15,499 - 10 - 133600a overall axial length of the seal holder is 3 inches and length of the extension past the shroud edge is 1 1/2 inches. The seal material is lead-based babbitt and the impeller shroud including the toothed portion is aluminum. The impeller is operated and gas is passed through the turboexpander as described in Example I. The gap between the toothed portion and the seal material is reduced by about 0.0021 inches over the gap that would occur with a conventional labyrinth seal. This reduction in the seal gap provides an increase in the efficiency of the turboexpander of 0.7 percent.
Now by the use of the labyrinth seal of this invention one can operate turbomachinery with increased efficiency. Although the labyrinth seal of this invention has been described in detail with reference to a specific embodiment and in operation in a turboexpander, those skilled in the art will recognize that there are other embodiments of the labyrinth seal of this invention and that the invention is useful with any type of turbomachinery.
D-15,499
Claims (13)
1. Turbomachinery with a labyrinth seal comprising:
(a) a rotatable assembly comprising (i) a shaft, (ii) a plurality of blades mounted on the shaft, said blades having a greater diameter at one axial end and a lesser diameter at the other axial end, and (iii) an impeller shroud attached to and encasing the blades from their lesser to their greater diameter so as to form a fluid flow passage, said shroud having an edge at the axial end of lesser blade diameter and having a toothed portion;
(b) a stationary housing spaced from the impeller shroud; and (c) an annular seal holder attached to the housing, situated between the housing and the impeller shroud adjacent the toothed portion, said holder positioning a seal member in a labyrinth sealing relationship with said toothed portion, and said holder having a tubular extension extending beyond said edge of the impeller shroud by at least 25 percent of the axial length of the seal holder, said extension extending axially beyond and spaced from that part of the housing to which said seal holder is attached;
whereby fluid expanded or compressed by the turbomachinery contacts the seal holder extension adjacent the region of lesser blade diameter.
(a) a rotatable assembly comprising (i) a shaft, (ii) a plurality of blades mounted on the shaft, said blades having a greater diameter at one axial end and a lesser diameter at the other axial end, and (iii) an impeller shroud attached to and encasing the blades from their lesser to their greater diameter so as to form a fluid flow passage, said shroud having an edge at the axial end of lesser blade diameter and having a toothed portion;
(b) a stationary housing spaced from the impeller shroud; and (c) an annular seal holder attached to the housing, situated between the housing and the impeller shroud adjacent the toothed portion, said holder positioning a seal member in a labyrinth sealing relationship with said toothed portion, and said holder having a tubular extension extending beyond said edge of the impeller shroud by at least 25 percent of the axial length of the seal holder, said extension extending axially beyond and spaced from that part of the housing to which said seal holder is attached;
whereby fluid expanded or compressed by the turbomachinery contacts the seal holder extension adjacent the region of lesser blade diameter.
2. The seal of claim 1 wherein the seal holder is attached to the housing at a flanged portion which is perpendicular to the axial length of the seal holder.
3. The seal of claim 1 wherein the part of the seal holder which extends past the edge of the impeller shroud is from 25 to 75 percent of the total axial length of the seal holder.
4. The seal of claim 1 wherein the part of the seal holder which extends past the edge of the impeller shroud is from 50 to 75 percent of the total axial length of the seal holder.
5. The seal of claim 1 wherein the turbomachinery is a turboexpander.
6. A method for controlling the clearance between rotating and stationary members of a turbomachinery labyrinth seal comprising:
(a) passing fluid through a passage formed by blades mounted on a rotatable shaft, said blades having a greater diameter at one axial end and a lesser diameter at the other axial end, and an impeller shroud attached to and encompassing the blades from their lesser to their greater diameter, said impeller shroud having a toothed portion and being spaced from a stationary housing, said fluid experiencing a pressure change and consequently a temperature change due to said passing;
(b) passing the fluid, outside of the passage and adjacent the region of lesser blade diameter, in contact with an extension of a tubular annular seal holder, said seal holder attached to the housing and situated between the housing and the impeller shroud adjacent the toothed portion and accomplishing this by providing said extension extending beyond said impeller shroud by at least 25 percent of the axial length of the seal holder, and extending axially beyond said spaced from that part of the housing to which said seal holder is attached; and (c) transferring heat between the fluid and the seal holder extension so as to cause the seal holder to expand or contract in response to said heat transfer said holder positioning a seal member in a labyrinth sealing relationship with said toothed portion.
(a) passing fluid through a passage formed by blades mounted on a rotatable shaft, said blades having a greater diameter at one axial end and a lesser diameter at the other axial end, and an impeller shroud attached to and encompassing the blades from their lesser to their greater diameter, said impeller shroud having a toothed portion and being spaced from a stationary housing, said fluid experiencing a pressure change and consequently a temperature change due to said passing;
(b) passing the fluid, outside of the passage and adjacent the region of lesser blade diameter, in contact with an extension of a tubular annular seal holder, said seal holder attached to the housing and situated between the housing and the impeller shroud adjacent the toothed portion and accomplishing this by providing said extension extending beyond said impeller shroud by at least 25 percent of the axial length of the seal holder, and extending axially beyond said spaced from that part of the housing to which said seal holder is attached; and (c) transferring heat between the fluid and the seal holder extension so as to cause the seal holder to expand or contract in response to said heat transfer said holder positioning a seal member in a labyrinth sealing relationship with said toothed portion.
7. The method of claim 6 wherein the fluid is passed through the passage from the greater to the lesser diameter and experiences a pressure decrease during the passage.
8. The method of claim 6 wherein the fluid is passed through the passage from the lesser to the greater diameter and experiences a pressure increase during the passage.
9. Turbomachinery with a labyrinth seal comprising:
(a) a rotatable assembly comprising (i) a shaft, (ii) a plurality of blades mounted on the shaft, said blades having a greater diameter at one axial end and a lesser diameter at the other axial end, and (iii) an impeller shroud attached to and encasing the blades from their lesser to their greater diameter so as to form a fluid flow passage, said shroud having an edge at the axial end of lesser blade diameter and having a tooth portion;
(b) a stationary housing spaced from the impeller shroud;
(c) an annular seal holder attached to the housing, situated between the housing and the impeller shroud adjacent the toothed portion, said holder positioning a seal member in a labyrinth sealing relationship with said toothed portion, and having a tubular extension extending beyond said edge of the impeller shroud; and (d) a conical take-up ring between the seal holder and the housing, said take-up ring contacting the housing on the radial outer side of the take-up ring at the greater diameter of the take-up ring, and contacting the seal holder on the radial inner side of the take-up ring at the lesser diameter of the take-up ring;
- 13a -whereby fluid expanded or compressed by the turbomachinery contacts the seal holder extension adjacent the region of lesser blade diameter.
(a) a rotatable assembly comprising (i) a shaft, (ii) a plurality of blades mounted on the shaft, said blades having a greater diameter at one axial end and a lesser diameter at the other axial end, and (iii) an impeller shroud attached to and encasing the blades from their lesser to their greater diameter so as to form a fluid flow passage, said shroud having an edge at the axial end of lesser blade diameter and having a tooth portion;
(b) a stationary housing spaced from the impeller shroud;
(c) an annular seal holder attached to the housing, situated between the housing and the impeller shroud adjacent the toothed portion, said holder positioning a seal member in a labyrinth sealing relationship with said toothed portion, and having a tubular extension extending beyond said edge of the impeller shroud; and (d) a conical take-up ring between the seal holder and the housing, said take-up ring contacting the housing on the radial outer side of the take-up ring at the greater diameter of the take-up ring, and contacting the seal holder on the radial inner side of the take-up ring at the lesser diameter of the take-up ring;
- 13a -whereby fluid expanded or compressed by the turbomachinery contacts the seal holder extension adjacent the region of lesser blade diameter.
10. The turbomachinery of claim 9 wherein the seal holder is attached to the housing at a flanged portion which is perpendicular to the axial length of the seal holder.
11. The turbomachinery of claim 9 wherein the part of the seal holder which extends past the edge of the impeller shroud is from 25 to 75 percent of the total axial length of the seal holder.
12. The turbomachinery of claim 9 wherein the part of the seal holder which extends past the edge of the impeller shroud is from 50 to 75 percent of the total axial length of the seal holder.
13. The turbomachinery of claim 9 wherein the turbomachinery is a turboexpander.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US007,479 | 1987-01-28 | ||
| US07/007,479 US4909706A (en) | 1987-01-28 | 1987-01-28 | Controlled clearance labyrinth seal |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1336005C true CA1336005C (en) | 1995-06-20 |
Family
ID=21726424
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000557522A Expired - Fee Related CA1336005C (en) | 1987-01-28 | 1988-01-27 | Controlled clearance labyrinth seal |
Country Status (7)
| Country | Link |
|---|---|
| US (1) | US4909706A (en) |
| EP (1) | EP0276839B1 (en) |
| JP (1) | JPS63235771A (en) |
| KR (1) | KR930008674B1 (en) |
| BR (1) | BR8800309A (en) |
| CA (1) | CA1336005C (en) |
| DE (1) | DE3883997T2 (en) |
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|---|---|---|---|---|
| DE69002064T2 (en) * | 1989-01-09 | 1993-12-23 | Northern Eng Ind | Fastening and arrangement of segment-shaped elements in turbomachinery. |
| JP3567064B2 (en) * | 1997-06-23 | 2004-09-15 | 株式会社 日立インダストリイズ | Labyrinth seal device and fluid machine provided with the same |
| JP4252785B2 (en) * | 2002-10-01 | 2009-04-08 | 株式会社パイオラックス | Piping connector and manufacturing method thereof |
| DE502006004968D1 (en) * | 2006-01-12 | 2009-11-12 | Sulzer Pumpen Ag | Turbomachine for a fluid with a radial sealing gap |
| US7625177B2 (en) * | 2006-08-31 | 2009-12-01 | Pratt & Whitney Canada Cororation | Simple axial retention feature for abradable members |
| DE102009053954A1 (en) * | 2009-11-19 | 2011-06-09 | Siemens Aktiengesellschaft | Labyrinth seal and method of making a labyrinth seal |
| US20160281727A1 (en) * | 2015-03-27 | 2016-09-29 | Dresser-Rand Company | Apparatus, system, and method for compressing a process fluid |
| CN105570184A (en) * | 2015-12-23 | 2016-05-11 | 三一环保科技有限公司 | Air seal structure and steam compressor thereof |
| US10822983B2 (en) * | 2018-02-06 | 2020-11-03 | Raytheon Technologies Corportation | Hydrostatic seal with abradable teeth for gas turbine engine |
| US11486498B1 (en) * | 2021-09-10 | 2022-11-01 | Hamilton Sundstrand Corporation | Dynamic sealing labyrinth seals |
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-
1987
- 1987-01-28 US US07/007,479 patent/US4909706A/en not_active Expired - Fee Related
-
1988
- 1988-01-27 JP JP63014817A patent/JPS63235771A/en active Granted
- 1988-01-27 BR BR8800309A patent/BR8800309A/en not_active IP Right Cessation
- 1988-01-27 DE DE88101192T patent/DE3883997T2/en not_active Expired - Fee Related
- 1988-01-27 EP EP88101192A patent/EP0276839B1/en not_active Expired - Lifetime
- 1988-01-27 CA CA000557522A patent/CA1336005C/en not_active Expired - Fee Related
- 1988-01-27 KR KR1019880000661A patent/KR930008674B1/en active IP Right Grant
Also Published As
| Publication number | Publication date |
|---|---|
| KR930008674B1 (en) | 1993-09-11 |
| KR880009186A (en) | 1988-09-14 |
| BR8800309A (en) | 1988-09-06 |
| DE3883997T2 (en) | 1994-01-13 |
| EP0276839B1 (en) | 1993-09-15 |
| EP0276839A2 (en) | 1988-08-03 |
| JPH0461987B2 (en) | 1992-10-02 |
| DE3883997D1 (en) | 1993-10-21 |
| US4909706A (en) | 1990-03-20 |
| JPS63235771A (en) | 1988-09-30 |
| EP0276839A3 (en) | 1990-02-07 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |